1. Field of the Invention
The present invention relates to a method for transferring a carbon film, including graphene, particularly relates to an efficient method for transferring a graphene film with low chemical and mechanical damages.
2. Description of Related Art
Carbon coatings ranging from sp3-bonded diamond films, diamond-like films with mixed sp3-bonding and sp2-bonding, to sp2-bonded graphene films and many others are of great interest and useful for many practical applications. Among them, the thinnest and most difficult to be handled or transferred from one substrate to the other is graphene films of only one atom or few atoms thick. Although the present invention relates to a method for transferring such a graphene film with low chemical and mechanical damage. The method is applicable to other carbon films including diamond films, diamond-like films, and other composite carbon films with or without metals of relevant dopants or additives.
The structure of a monolayer graphene film is formed by hexagonal rings of sp2-bonded carbon atoms that are tightly packed into a two-dimensional honeycomb lattice. The general term of graphene includes one layer of monolayer graphene, multiple layers of monolayer graphene of different sizes stacking in a variety of stacking orders, and graphene structures with one or more layers of monolayer graphene deposited horizontally on a substrate or growing vertically from a substrate as a standing graphene.
Graphene has excellent optical, electronic, and mechanical properties, and is applicable to transparent conductive layers, conductive composites, or flexible electronics due to its transparent nature. Also, it may be applied in a capacitor, a lithium electrode, or a mechanical reinforced composite.
Many graphene products are formed by transferring graphene from where it is synthesized to a application substrate. Furthermore, some products require stacking a plurality of graphene films in a manner of layer-by-layer transferring. Currently, a preferable method for synthesizing a graphene film is the thermal chemical vapor deposition, wherein the graphene film is formed on a catalytic metal and then adhered with polymethylmethacrylate (PMMA). Therefore, using an etching process, the catalytic metal is separated from the graphene film adhered thereon, thereby transferring the graphene film onto PMMA. Next, a target substrate is laminated with the PMMA adhered with the graphene film, and then the PMMA is removed by heat, ultraviolet (UV) light, gas (H2 and N2), or acetone, to transfer the graphene film onto the target substrate, thus achieving transferring of the graphene film.
The above-mentioned method for transferring a graphene film may work efficiently. However, during the transferring of the graphene film from the catalytic metal to the target substrate, several chemical solution etching and mechanical impression processes are required, causing the graphene film to crack. Accordingly, it is desirable to develop a method for transferring a graphene film with efficiency, high yield, and low stress to exploit more applications of the graphene film.